MTN gives extra contract without consent and forces you to pay

MTN offerred me a Sim card contract online for R150 and instead sent me 2 sim cards for R470. It has since been a struggle to return one as the branches, apparently can not do anything about it.If the online service is in no way connected to MTN, then why sell their contracts. MTN Limpopo mall and MTN Schoeman street Polokwane are unable to even view my contracts.